Severing machine



March .1944.

JACOBSEN SEVERING MACHINE Filed Jan, .2 194? 4 Sheets-Sh 2 WW an sq v 3 Ms w l.

Patented 7,

1 UNl'l ED STAT ES PATENT orslce Arthur J. Jacobsen. Oak Park, Ill. I Application January 29, 1942, Serial No. 428,677 21 Claims. (c1. 51-98) The prsent invention relates to a machine for cutting or severing hard materials, such for example as metal parts, by abrasive action, and is an, improvement of the machine disclosed in my Patarea thereof, and to concentrate the coolant andcause it to penetrate the cut in the work under pressure whereby to preserve the form and increase th life of the element, and to avoid deleterious changes in the metallurgical and physical characteristics of the work.

A further object is to provide new and improved means for rigidly supporting, locating and clamp-- ing the work at both sides of the grinding element and close to the line of cut.

Other objects and advantages will becomegapparent as the description proceeds. v

In the accompanying drawings,- Figure 1 is an end elevational view, partially in section, of a metal severing machine embodying the features of my invention.

\ Fig. 2 is a plan view, partially in section, of the machine.

Fig.3 is an axial sectional view of the motor drive taken along line 3-3 of Fig. 2.

scribein detail the preferred embodiment, but it is to be understood that I do not therebyintend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the inventionas expressed in the appended claims.

Referring more particularly to the drawings,

"the severing machine, constituting the exemplary embodiment of the present invention, is especially adapted for cutting or severingwer'y hard materials, such for example as tool steels and alloys,

by the use of a thin abrasive rotary cutting ele-' ment or disk T at a high rate of speed.

The. work, which may be in; the form of a bar W; is mounted on a stationary support or table I l, and is located and securedby a heavy clamp- Fig. 4 is a fragmentary vertical sectional view through the work support, taken along line 4-4 of Fig. l.- a

Fig. 5 is an axial sectional view of the tool spindle structure, taken along. line 55 of Fig. 1.

Fig. 6 is a view of the inner face of one of the impeller disks associated with the grinding element.

Fig. 7 is an enlarged fragmentary sectional view of the grinding element and impeller assembly.

Fig. 8 is a fragmentary 'sectional view taken substantially along line 8-8 of Fig. 2, and illusr trating the work supporting and clamping-means. Figs. 9 and 10 are sectional detail views taken respectively along lines 99 and Iiiof Fig. 8. While the invention is susceptible of various modifications and alternative constructions, I have shown inthe drawings and will herein demg pressure, but without deflection, in position against two rigid and sturdy fence or guide blocks 2 at opposite sides of the grinding disk T. The grinding disk is movable transversely into and through cutting engagement with the work.

A suitable coolant, such as water, in an abundant amount is directed by an impeller associated with the grinding diskT in sheet form evenly over both side faces of the disl-nfrom the center tothe outer periphery, and serves to prevent the disk from heating up and expanding, and hence to insureminimur'n wear and a long life. The binder for the abrasive particles in the disk T does not soften up, and the disk retains its straight form and can be worn down in use to its minimum size. The coolant also plays upon the Work and is caused to penetrate the cut to provide a free running grinding disk; Such penetration is efiected'by hydraulic pressure which is created by the rotation of the disk at high speed, and which increases as the speed is increased.

Penetration is further promoted by entrainment of coolant in the pores of the abrasive element. As a. result, burnlng of the work is avoided, and

metallurgical and physical changes, such as.

, having legs 8 adapted to rest on a suitable foundation. The interior of the base. 3 constitutes a large reservoir 9 adapted to contain a suitable coolant I0, such as water. The work support I consists of a horizontal T-shaped frame mounted in the top of the base 8 and spaced from the side walls 6 and 'l. The rear end of the 'frame 2 is 2 i coextensive in width with the base a, and constitutes a base extension H. A spaced wall or outboard support I! is attached to the base extension II, and is connected through tie bars I! to the lower portion of the base I. The rear wall I of the base 3 and the spacedwali i2 thus define a compartment l4.

Mounted in the top of the base 8 alongside the work support I to receive the spent coolant are two settling tanks ll. Suitable angle bars II attached to the base walls! and underlie and support the ends of the tanks IS. A secondary settling tank" i mounted in i4 at a level below the tanks il and is supported byangle bars II on the spaced walls 5 and II. coolant from the tanks li-overilows through inclined ducts it into the tank IT. The ducts I! extend through openinss III in the rear base wall hand their upper ends project somewhat above the bottom walls of the tank l5. Coolant from the secondary tank I! flows from near the top thrcimh an opening 2| in the wall a into the reservoir 0. Most of the sludge will collect in the bottom of the tanks i5, and any suspended solids passing over with the coolant through the ducts ll will settle out in the tank II so that the coolant in the reservoir 8 will be clear.

The guide blocks 2 which constitute the work fence are disposed end to end in slightly spaced relation at opposite sides of a cutting slot 22 in v the table I to receive the periphery of the disk T,

and are accurately located by keys 23 engaging in akeyway'll in the top of. the table and rigidly secured in position by means of clamp bolts 24 extending thro the keys into threaded engagement with the table. The blocks present a guide face or surface 2! on one vertical side for locating the work accurately in position during the cutting operation. The contiguous ends of the blocks 2 have two edges 2' which are spaced apart in the plane of the guide face 2! just enough to receive the grinding disk T, and which are relieved rearwardly by diverging surfaces 21 to provide clearance for the coolant. As a result, the work is supported and backed up to resist the cutting action, and to permit a strongclamping force without work deflection at closely spaced points immediately adjacent the opposite edges of the cutting periphery of the grinding disk. Thus, the work is clamped closely to the line of the compartment 1 assasse the sides of the slot converge along their upper edges toward the free end, and are undercut at a to provide clearance, facilitating the flow of coolant and concentrating it under pressure against the work at the point of cut.

Pivotally connected to the forward end of the "block at 88 is a draw bar I! which extends loosely through an upstanding bracket arm 38 adjustably bolted on a clamp bracket 38 on the front of the base I. A heavy coiled compression sprin 4. encircles the draw bar 31, and abuts at oppo- Site ends. p tively, against the forward end of the clamp bar 28 and the opposed bracket arm ll. The spring 40 acts to urge the bar toward the fence I to clamp the work quickly and with a heavy pressure. By reason of the rigid construction of the fence, no deflection of the work or of the clamp parts occurs.

To release the work after the cutting operation and to permit indexing thereof or the insertion of new work. suitable means is provided for retracting the clamp bar 28 against the pressure of the spring 40. This means comprises a bellcrank lever 4| pivotally mounted on the bracket 39 between two ears 42. The vertical arm of v, the bell crank lever 4i receives the forward end cut so that very thin pieces of work canbe severed.

To provide means for securely clamping the work against the fence blocks 2. a rectangular clamp bar 28 is slidably mounted on the top of the work table I for movement transversely of the blocks. Preferably, the clamp bar is redtangular in cross section and formed in opposite sides with longitudinal guide grooves 29. The block is confined for longitudinal adjustment against the table I by two parallel guide bars 30 engaging in the grooves 29. Preferably, each guide bar consists of two superimposed plates bolted to the top of the work table I, and with the upper plate projecting along one edge beyond the lower plate to provide a tongue 3!. The inner end of the clamp bar 28 is bifurcated to provide two closely spaced clamping jaws 32 adapted for engagement with the work at opposite sides and clowly to the grinding disk T. The .space between the jaws constitutes a slot 33 adapted to receive the peripheral margin of the grinding disk T and also to direct coolant to the cutting zone. The closed end of the slot 33 is formed with a downwardly inclined root surface 34, and

of the draw bar 31, and coacts with an adjustable" stop nut 43 threaded on the latter. A roller 44 is seated between the lever 4| and the nut 43 to insure full surface engagement in diiferent angular positions of the lever. The horizontal arm of the bell crank lever H is pivotally connected through a link 4! including a turn buckle 46 to a foot treadle mounted on the lower portion of the machine base I.

By the foregoing arrangement, the pressure of the spring 44 may be adjusted by shifting the position of the bracket arm 18 along the bracket 39. Also, the range of movement of the clamp bar 28 may be adjusted to suit the width of each particular piece of work. This is accomplished by slightly separating the arm 38 and the vertical arm of the lever 41, and then adjusting the nut'43 to locate the jaw 32 substantially in clamping position. Upon reelasing the lever 4i fbr engagement with the arm 38, a slight overtravel is permitted so that the full force of the spring pressure is available.

The grinding element T and the coolant im peller 41 are secured on one end of a tubular spindle 48 against an end shoulder 49 by means of a clamp nut 50. The spindle 48 is suitably joumaled at spaced points in anti-friction bearings 5i and 52 in a tubular sleeve or housing 53 mounted on the free end of a rocker arm 54. Suitable end plates 55 and 58 with oil seals 51 are removably secured to opposite ends of the spindle sleeve 53 to close the latter.

The rocker arm 54 is mounted for oscillation on an axis extending generally parallel to the fence 2. In the present instance, the rear end of the rocker arm 54 is formed with a swivel sleeve 8 rotatable on a bearing sleeve 59 forming part of a bell housing 60 on an electric drive motor ii. The outer end of the sleeve 59 is supported by an outboard bracket 62 mounted on the base extension I l.

The electric motor 8| is also mounted on the drive for the grinding disk T. An idler pulley Fixed on the outer ends of the spindle 48 and the motor shaft 88 are two multiple groove pulleys 88 and 87 which are connected by a plurality of V-belts 68 toprovide a high speed rotary rotatably mounted on a bracket III engages the undersides of the top flights of, the belts 88 to maintain them under proper tension. The bracket I is pivotally secured at one end by means of a bolt .II to one side of the rocker arm 84, and is adapted to be clamped indifferent angular positions at the other end by a bolt I2 extending through an arcuate slot 73. Since the pulley 81 is located on the pivotal axis of the rocker arm 84, the belt drive for the spindle 48 will be unaffected by the pivotal or swinging movement of the grinding disk T into and out of cutting engagement with the work. I

To provide means for oscillating the grinding disk T, a hand bar I2 is rigidly secured in a boss I8 on the spindle housing 88, and projects outwardly and forwardly for convenient grasp by the operator. A counterweight I4 is connected to the swivel sleeve 58 oppositely to the bar I2 and tends to elevate the grinding disk T away from the work support I. Downward movement of the grinding disk '1 into and through cutting engagement with the work is adapted to be efiected manually by. grasping and lowering the bar 52 against the force of the counterweight 14. To

limit the downward swinging movement of the disk T, a stop p n 75 with an adiusting handle I8 is threaded through a block 11 bo ted to the rocker arm 58 for end engagement with an abutment I8 on the base extension I I.

Mounted on the work table I and enclosing the grinding disk T and impeller 41. is a guard or hood l8. One side wall of the hood 18 is formed with an arcuate slot 88 concentric with the pivotal axis of the rocker arm 54, and receiving the spindle 48 between the impeller 41 and the adjacent end plate 55 of the spindle housing 53. The other side wall of the hood 18 is hinged to constitute a door 8I adapted to be opened when access to the grinding disk T is required. Both side walls of the hood I8 are formed in their lower' edges with notches oropenings 82 to receive the work in normal operation and to receive the fence blocks 2. Similarly, the lower forward edge of the peripheral wall of the hood is formed with a notch 83 to accommodate the clamp bar 28.

To provide means for su plying coolant from the reservoir 9 to the-impeller 41, the spindle 48 is formed with an axial'passage 88.. One end opens through a plurality of radial ports 88 to the impeller 41. The other end of the passage 84 has a swivel connection with a supply pine 88. The connection. consists of a swivel tube 81 journaled in a bearing sleeve 88 pressed into a counterbore 89 in the passage 84. The outer end of the tube 81 is connected by an elbow 80 to the pipe 88. A coolant pump 9| mounted in the compartment I l has an inlet line 82 opening from the lower part of the reservoir 8, and discharges to a flexible conduit 83 connected to the pipe 88. Preferably, the pipe 88 extends along the rocker arm 54, and is connected to the flexible conduit 83 substantially on theswivel axis.

of the sleeve 58 so that the connection is not appreciably afiected by the pivotal or oscillatory movement of the grinding disk T. The pump 8i may be driven by any suitable means, such as an electric motor 84. v

The impeller 41 serves to direct coolant from the spindle passage 84 uniformly-in thin sheets free running in the work in direct contact with and outwardly over the entire side faces of the grinding disk '1 under extremely high pressure. In it preferred form, the impeller 41 comprises two similar disks 85 and 88 securely clamped against opposing sides of the central-or hub portion of the grinding disk '1 for rotation therewith. More particularly, the grinding disk T is confined between the impeller disks 85 and 88, and the assembly is suitably keyed to the spindle 48. A spacer sleeve 81 on the spindle 48 extends through the end plate 88 into abutment with the inner raceway of the ad- ,iacent bearing BI, and engages the inner impeller disk 88 to locate the assembly in proper relation to the cutting slot 22 in the work support I.

- Each of the impeller disks comprises a plurality of peripherally spaced vanes or ribs 88 on the inner side face directly contacting the grinding disk T. These ribs are eccentrically disposed relative to the axis of rotation, and are generally crescent-shaped with theconvex sides arranged to force the coolant outwardly upon rotation in the direction of the arrow in Fig. 6. The interdental passages 98 between the vanes 88 open at their inner ends to a central annular space I88 about the spindle 48 and in communication with the radial ports 88, and at their outer ends to an annular groove IOI defined by a marginal annular flange I82.on the disk. The marginal ilange I82 is slightly spaced from the adjacent side of the grinding disk T to define therewith an uninterrupted peripheral outlet opening or port I88 for the coolant, and the end face I04 of the flange is inclined radially outwardly toward the grinding disk so as to cause the coolant to issue in, a thin sheet in direct contact with the side surface of the grinding disk.

Coo ant under pressure is supplied in an abundant amount and is caused by the impeller 47 to stream outwardly over both sides of the grinding disk T. A a consequence, the grinding disk T is virtuallvflooded ith coolant and is being severed. The grinding disk thus is prevented from becoming heated so that the bonflng material for the abrasive part cles does not soften up, and the disk re.- mains straight throughout its useful life. The coolant is also caused 'to penetratethe cut in the work. .therebypreventing burning and the formation of spots, cracks and checks. Such penetration is effected in part by entrainment of coolant with the grinding disk T into the cut. The coolant which is flung through centrifugal force from the grinding disk T is caused to impinge against the interior of the hood I8 and is directed by a curved channel-shaped deflector I08 in a I concentrated stream under considerable pressure against the work at the point of cut.

In particular, the deflector I 05 directs the high velocity stream of coolant to the slot 33 in the clamp ba'rZB from which the coolant issues and impinges against the work at both sides of the grindin rr disk T.

It will be seen that I have provided a novel and advanta eous machine for serving workpieces of hard material. The machine is capable of accurate and high speed operation. The grinding element retains its correct form and has a long life. The work does not suffer any deleterious metallurgical and physical changes, and the seversd ends have a smooth finish and are free of burrs.

I claim as my invention:

1. A material serving machine comprising, in combination, a base, a work support on said base against said fence in and having a narrow cutting slot, a fence on said support extending generally transversely of said slot and defining a recess in registration with said slot, means for clamping the workpiece position across said recess, a rotary spindle mounted on said base for oscillatory movement about a fixed axis toward and from said support, a thin abrasive disk fixed on one end of said spindle for swinging movement therewith and in registration with said slot and recess, two circular impeller disks rigidly mounted on said spindle ih direct abutment against opposite sides of said abrasive disk, each of said impeller disks having a plurality of uniformlyyperipherally spaced passages opening outwardly and having a marginal flange slightly spaced from said cutting disk and defining an annular groove in communication with said passages and opening peripherally at said abrasive disk to discharge a continuous sheet of coolant, and means for supplying coolant under pressure to said passages.

2. In a material severing machine, in combination,'a frame having a flat horizontal work supporting surface formed with a fence locating groove, two alined fence blocks mounted on said surface in closely spaced end to end relation along said groove, each block being formed in the under side with a longitudinal keyway in registration with said groove, a key pressed in said keyway and engaging in said groove, and clamp bolts extending through said blocks and said keys into threaded engagement with said frame to secure said blocks in position.

3. In a material severing machine, in combination, a work support formed with a cutting slot, two fence blocks mounted on said support in end to end relation respectively at opposite sides of said slot and defining a recess in registration with said slot, a clamping bar mounted on said support for endwise reciprocation toward and from said fence blocks and the leading end of said bar being bifurcated to define closely spaced jaws separated by an intermediate clearance slot in registration with said recess, said clearance slot being tapered toward the free end and being undercut, means for actuating said bar in opposite directions, and a thin grinding disk mounted for movement toward said support into said slots and recess to sever the work.

4. In a material severing machine, in combination, a work support, afence on said support for locating the work, means for severing the work when in position against said fence, a clamping member reversibly movable for clamping said work against said fence during the severing operation, a bracket arm mounted on said support for adjustment toward and from said fence, spring means interposed between said clamping member and said arm for urging said member into clamping engagement with the work, a bell crank lever pivotally mounted on said arm, means coacting with said bell crank lever for limiting 'the movement of said member toward the work, and means for oscillating said lever to retract said member from said work. I

5. In a material'severing machine, in combination, a base, a work support on said base, a fence on said support for locating the work, a material severing element mounted on said base for movement toward and from said support to sever the work, a reciprocable clamping bar mounted on said support for movement transversely of said fence to clamp the work in position, a drawbar secured to the outer end of said clamping'bar, spring means acting on said clamping bar to ill) urge the latter toward the work, a bell crank,

lever pivoted on said base and receiving said drawbar through one arm, a nut adiustably secured on said drawbar for engagement with said arm to limit the forward movement of said clamping bar, a roller interposed between said arm and said nut, and means connected with the other arm of said lever for oscillating the lever to withdraw said clamping bar from said work against the pressure of said snrinr means.

6. In a material severing machine, an impellercomprising, in combination, a rotary spindle, an abrasive cutting element secured to said spindle for rotation therewith, and two impeller disks secured to said spindle at opposite sides of said cutting element and for rotation therewith, each of said disks coacting with said element to define a coolant chamber and having an outer peripheral edge spaced from said element to provide a restricted peripheral outlet arranged to discharge a continuous sheet of coolant under high pressure from and chamber outwardly over the adjacent side of said element and in intimate contact therewith, and means for supplying coolant to said chamber.

7. In a material severing machine, an impeller comprising, in combination, a rotary spindle, an abrasive cutting element secured to said spindle for rotation therewith, and two impeller disks secured to said spindle at opposite sides of said cutting element and for rotation therewith, each of said disks coacting with said element to define a coolant chamber and having a plurality of angularly arranged vanes in said chamber contacting the adjacent side of said element, the outer peripheral edge of each disk being spaced from said element to provide an outlet for said chamber through which coolant is adapted to be discharged by centrifugal force in a continuous sheet outwardly over the adjacent side face of said element, and means for supplying coolant to said chamber.

8. In a material severing machine, an impeller comprising, in combination, a rotary spindle, an abrasive cutting element secured to said spindle for rotation therewith, and an impeller disk secured to said spindle at one side of said cutting element and for rotation therewith, said disk being formed on one side with a plurality of crescent-shaped vanes about the axis and extending toward the periphery, a peripheral flange on said disk and spaced from said element to define a continuous discharge opening, and means for supplying coolant through said spindle to the space between said element and said disk, said vanes serving to throw the coolant outwardly through said opening at a high'pressure and in a continuous sheet to flood the entire adjacent side face of said element.

9. In a material severing machine, a rotary spindle having an axial coolant supply passage opening at one end through radial ports, a thin rotary grinding disk secured to said spindle, two similar impeller disks secured to said spindle at opposite sides of and in direct contact with the hub portion of said disk, each of said impeller disks being formed with a series of peripherally spaced impeller vanes in direct contact with the contiguous side of said grinding disk to define flow passages extending generally outwardly toward the periphery, the inner ends of said passages being in communication with said ports, the outer periphery of each impeller disk being spaced from said grinding disk to define an annular outlet port in communication with the outer ends of said passages, whereby in the rotation of said spindle coolant from said ports is flung outwardly by said vanes under high pressure and caused to issue in a thin uniform sheet over and in direct continuous contact with the contiguous side of said grinding disk.

11. In a material severing machine, in combination, a work support adapted to locate and support the work in a cutting position, a rotary grinding disk movable into and out of cutting engagement with the work, and an impeller associated with the hub of said disk for directing coolant under a relatively high pressure and in thin continuous sheets radially outwardly over and in direct contact with the opposite side faces of said disk, said impeller having substantially continuous peripheral outlets through which said coolant is adapted to issue and which outlets have beveled edges inclined radially outwardly toward the side faces of said disk.

12. In a material severing machine, in combination a work support adapted to locate and support the work in a cutting position, a rotary grinding disk movable into and out of cutting engagement with the work, and an impeller associated withthe hub of said disk for directing coolant under a relatively high pressure and in thin streams radially outwardly over and in direct contact with the opposite side faces of said disk,

cillation of said rocker arm toward and from said support, a counterweight integral with said rocker arm and tending to move said cutting element away from said support.

15. A material severing machine comprising. in combination, a base, a work support on said base, a rearward extension on said base, an electric motor mounted on said extension and having a bell housing with a tubular sleeve, the motor shaft extending through and being Journaled in said sleeve, a rocker arm having a swivel sleeve on one end rotatably supported on said tubular sleeve, an outboard support on said extension for said shaft and acting to confine said swivel sleeve in position, a spindle mounted in the other end of said rocker arm in parallel relation to said shaft, belt drive means connecting said shaft to said spindle, a rotary cutting element mounted on said spindle and being movable through oscillation of said rocker arm toward and from said support,

a counterweight integral with said rocker arm and tending to move said cutting element away from said support, and adjustable stop means for limiting the movement of said cuttingelement toward said support.

16. A material severing machine comprising, in combination, a base, a work support on said base,

an electric motor mounted on said base andhaving a housing with a tubular sleeve. the motor shaft extending through and being Journaled in said sleeve, a rocker arm having a swivel sleeve rotatably supported on said tubular sleeve, a

spindle mounted in said rocker arm in parallel relation to said shaft. belt drive means connecting a hood enclosing said disk and impeller, and

means in said hood for directing a concentrated stream of-the coolant leaving saiddisk against the work at the point of cut. 7

13. In a material severing machine, in combination, a work support, a fence on said support formed with a central recess and arranged to locate the work in position, a clamping bar movable on said support transversely of said fence and being formed in the forward end with a slot having an inclined root surface and in registration with said recess, a thin rotary grinding disk mounted for movement transversely of said fence into and out of saidrecess and slot, a hood enclosing said recess, means for directing coolant against opposite sides of said disk, and deflector means in said hood fpr directing coolant thrown from said disk through centrifugal force into and through said slot in a concentrated stream against the work at the cutting zone,

14. A material severing machine comprising, in combination, a base, a work support on said base, a rearward extension on said base, an electric motor mounted on said extension and having a bell housing with a tubular sleeve, the motor shaft extending through and being journaled in said sleeve, a rocker arm having a swivel sleeve on one end rotatably supported on said tubular sleeve, an outboard support on said extension for said shaft and acting to confine said swivel sleeve in position, a spindle mounted in the other end of said rocker arm in parallel relation to said shaft, belt drive means connecting said shaft to said spindle, a rotary cutting element mounted on said spindle and being movable through ossaid shaft to said spindle, an idler pulley on said rocker arm for tensioning said belt drive, a rotary cutting element mounted on said spindle and being movable through oscillation of said rocker arm toward and from said suppont, and means tending to move said cutting element away from said support.

17. A material severing machine comprising, in combination, a base, a work support on said base, a rocker arm mounted on said base for pivotal movement about a fixed axis, a tubular spindle mounted in said rocker arm in'parallel relation to said axis; means for driving said spindle, a rotary cutting element mounted on said spindle and being movable through oscillation of said rocker arm toward and from said support,- a pipe mounted on said arm for movement therewith and being connected at one end to theinterior of said spindle, a flexible coolant supply conduit connected to the other end of said pipe substantially in line with said axis, and an impeller mounted on said spindle in association with said element, and-connected to receive coolant from the interior of said spindle and to discharge the coolant over said element.

18. In material severing machine, in combination, a horizontal work support formed with a cutting slot, a fence on said support for locating the work to be severed in position across said slot, a clamping bar mounted on said support for movement longitudinally of said slot into and out of engagement with the work, the forward end ,of said bar being formed with spaced clamping jaws arranged to engage the work at opposite sides of said slot, a rotary disk grinding element mounted for oscillation through cutting engagement with the work, means for flooding both sides of said grinding element with an abundance of a cooling liquid at high velocity and pressure, a hood. enclosing said grinding element, and a deflector in said hood f0r directing cooling liquid from said element in a concentrated stream under pressure through the space between said Jaws and into said slot to penetrate the cut in the work during the severing operation 19. In a material severing machine, in combi-.

nation, a work support adapted to locate and support the work in a cutting tion, a rotary grindlns disk movable into and out oi cutting engagement with the work, and an impeller associated with the hub of said disk for directing coolant under a relatively high pressure and in thin streams radially outwardly over and in direct contact with the opposite side faces of said disk, and means for directing a concentrated stream of the coolant leaving said disk against the work at the point 01 cut.

20. In a material severinz machine, an impeller comprising, in combination, a rotary spindle, an abrasive ,di'sk secured to said spindle for rotation therewith. an impeller disk secured to said spindle at one side or said abrasive disk and for rotation therewith, one side face of sad impeller disk being formed intermediate its inner and outer circumierential edges with a plurality oi peripherally spaced vanes extending generally outwardly and inclined to the radial, said vanes contacting the contiguous side iace oi said abrasive disk and serving to deilne a series of spiral passages, and means for directing coolant to the inner ends of said passages, the coolant from the outer ends of said passages being adapted to issue in a thin sheet irom between said abrasive disk 3:15? the outer peripheral edge 0! said impeller 21. In a material severing machine, an impeller sages, and means tor directing coolant to the inner ends or said passages, the coolant from the outer ends of said passe-lee being adapted to issue in a thin sheet from between said abrasive disk and the outer peripheral edge of said impeller disk, said outer edge having a side iace spaced from and inclined radially outwardly toward said disk to define the outlet for said coolant.

J JACOBSEN. 

